directly related to "buying a pig in a poke" :)
people used to buy live piglets at the market and the seller would put them in a burlap sack to be carried home. Unscrupulous sellers would put a cat in the bag instead. "who let the cat out of the bag" means to let others in on a secret...
Ok, I've read a few really good ones lately and I know you guys have to have some more.
From BYC I heard "nothing like a meal that comes with a free hat"
and just this morning I heard "knee-high to a grasshopper's butt" to describe a short person.
so what else ya got?